This invention relates to two-wheeled dolly units used by U.S. military forces to tow shelter units from one geographical location to another. Such shelter units are usually large box-like containers approximately seven feet wide, seven feet high, and fifteen feet long. They are used for such purposes as emergency hospital buildings, electronic radar equipment enclosures, and temporary command headquarters buildings. Each shelter has skids on its bottom surface for support of the shelter on the terrain. At each of its ends the shelter is equipped with fittings for attaching the shelter to a two-wheeled dolly when it is desired to tow the shelter to a new geographical location. The dollies give the shelter the mobility of a trailer.
Certain preparations are necessary to put the shelter into the so-called "towing" mode. One dolly is moved into position at the front end of the shelter; later, or simultaneously, the other dolly is moved into position at the other (rear) end of the shelter. Each dolly is affixed (attached) to the shelter, after which a fluid cylinder mechanism on each dolly unit is actuated to lift the shelter away from the ground surface, usually about 17 inches. A towbar at the frontmost dolly is attached to a military truck for enabling the dolly-shelter assembly to be towed to a new geographical location.
At the destination the fluid cylinder mechanisms on the dolly units are actuated to lower the shelter to the ground. The dolly units are disengaged from the ends of the shelter and bolted together into a four wheel package for towed transport to storage or another shelter requiring relocation.
Over the years the shelter units have been used for housing heavier types of equipment. Accordingly the dolly units have had to be redesigned as more massive and heavier structures, compared to the earlier dolly units. Some of the two wheeled dolly units, built or contemplated, weigh upwards of 1000 pounds (2000 pounds per dolly set). Due to the large dolly weight it becomes difficult to manually maneuver the dolly units preparatory to hook-up to a shelter unit. Considerable time and effort is usually required to precisely align the lifter elements on the dolly with the lift fittings on the shelter.
Another difficulty is presented by the nature of the fluid cylinder mechanisms used on existing dollies to lift the shelter unit away from the ground surface. Each dolly is usually provided with two hydraulic cylinders connected to a hand pump. The work effort is such that many human arm strokes are required to operate the pump the necessary length of time to pressurize liquid and deliver the required liquid quantities to the cylinders. Often more than 100 strokes of the pump are required.
The above difficulties result in a considerable time expenditure for attachment of the dolly units to a shelter and lifting of the attached shelter to an elevated position suitable for towing to a new location. Often twenty minutes or more are required to complete the attaching-lifting operation. Under battle conditions the soldiers might not have such a period of time; the shelter might then have to be abandoned.
The present invention relates to mechanisms for decreasing the time required to accomplish the operations of attaching the dolly units to the shelter and raising the shelter to the transport mode. To decrease the time required for attaching each dolly unit to a shelter I propose to equip each dolly unit with a motorized wheel assembly. Each motorized assembly comprises an air-operated motor having a drive connection with an auxiliary ground wheel. The tractive action of this auxiliary wheel augments the efforts of the soldiers required to maneuver the dolly unit back and forth into precise alignment with the lift fittings on the shelter. It is believed that by using the auxiliary motorized wheel assembly the soldiers will be enabled to accomplish the dolly-shelter attachment operation in a shorter time period (compared to the time required without using the motorized wheel assembly).
To decrease the time required for raising the attached shelter to the towing mode I propose to modify the mechanism used to pressurize the shelter lift cylinders. The proposed modification involves substitution of a motor-operated pump for the manual pump used under conventional practice. Preferably the pump will be powered by an air motor. The basis for the proposed substitution is the fact that military trucks used for towing shelters are equipped with on-board air compressors. It is believed that such compressors can deliver energy to an air-operated motor at a comparatively fast rate, compared to the rate of energy delivery achieved by human force on a pump operator (handle). Use of compressed air for energizing an air motor will necessitate running a compressed air hose from the air compressor on the truck to an air motor on each dolly. I contemplate that a single air hose will be used to supply compressed air to the motors for the hydraulic pump and motorized wheel assembly.